PNP/Cr(Ⅲ)配合物催化乙烯齐聚性能的研究

Ethylene Oligomerization Catalyzed by PNP/Cr(Ⅲ)Complexes HUANG Xumeng,FAN Haonan

合成并表征了N-二苯基膦基-1-乙基-1-苯基膦基-环戊胺(L1)、N-二苯基膦基-1-异丙基-1-苯基膦基-环戊胺(L2)和N-二苯基膦基-1-叔丁基-1-苯基膦基-环戊胺(L3)3种双膦胺(PNP)配体,考察了PNP/Cr(Ⅲ)配合物催化乙烯齐聚的性能,研究不同取代基在控制乙烯选择性三聚/四聚催化性能中的作用。通过密度泛函理论(DFT)计算,充分探讨了基于L1配体的催化体系的吉布斯自由能分布,结果表明:L1—L3配体组成的催化体系,具有催化活性高和C6选择性高的特点;L2配体组成的催化体系,在4.0 MPa和50℃时,催化活性可达1.36×10^(6) g/(mol·h);相比于路径1和路径2,路径3(三聚途径)具有相对较低的能垒,在热力学上更有利于乙烯三聚,这与实验结果一致。

Three bisphosphoamine(PNP)ligands,N-diphenylphosphonyl-1-ethyl-1-phenylphosphonyl-cyclopentamine(L1),N-diphenylphosphino-1-isopropyl-1-phenylphosphonyl-cyclopentamine(L2)and N-diphenylphosphino-1-tert-butyl-1-phenylphosphonyl-cyclopentamine(L3)were synthesized and characterized in our current study with an intended purpose to investigate the performance of PNP/Cr(Ⅲ)complexes in catalytic ethylene oligomerization and study the role of different substituents in controlling the selective ethylene tri-/tetramerization performance.Through density functional theory(DFT)calculation,the Gibbs free energy profiles of the L1 ligand-based catalytic system was thoroughly explored.The results showed that the catalytic system composed of L1-L3 ligands had high catalytic activity and high C6 selectivity;the catalytic activity of the catalytic system composed of L2 could reach 1.36×10^(6) g/(mol·h)at 4.0 MPa and 50℃;compared with path 1 and path 2,trimerization path 3 had a relatively low energy barrier and was more conducive to ethylene trimerization in thermodynamics,which is consistent with the experimental results.